Method for forming a calibration line in an infrared gas analyzer

Abstract

A forming method for a calibration curve in an infrared gas analyzer. The forming method minimizes the systematic error that occurs in the infrared gas analyzer improves measuring precision. The forming method modifies a method in which gases having different concentrations are supplied to an infrared gas analyzer. The gas analyzer has the outputs corresponding to the gas concentrations, and samples the gas concentrations as a plurality of points, the number of which is not less than four. A calibration curve is approximated by up to a fourth-order polynomial using a method of least squares based upon the measured values of not less than 4 points thus sampled. In carrying out the above-mentioned polynomial approximation, an inverse number of the square of the divided ratio at each point of the calibration curve is used so as to carry out a weighting operation.

What is claimed is:  
     
       1. A method for forming a calibration curve in an infrared gas analyzer, the infrared gas analyzer: 
       being supplied with gases having different concentrations,  
       having outputs corresponding to the concentrations of the gases,  
       sampling the gases as a plurality of at least four points,  
       measuring concentrations of the sampled gases, and  
       approximating a calibration curve with a fourth-order polynomial based upon the measured concentrations,  
       said method comprising the steps of:  
       computing a weighted coefficient equal to an inverse of the square of a divided ratio of the measured concentrations; and  
       multiplying said calibration curve by said weighted coefficient at each measured concentration.